This invention relates to an assembly for use in a machine such as a motor or compressor for preventing fluid leakage from occurring in the spaces between a movable rod and frame of the machine when the machine is in an inactive or static condition such that the rod is motionless.
Packing ring assemblies for preventing fluid leakage between the movable rod and frame of a machine have, generally speaking, long been in use in the prior art. Such prior art assemblies are shown and described in detail in Bulletin No. TBP-76 published by Dover Corporation/C. Lee Cook Division, P.O. Box 1038, Louisville, Ky. 40201. While such ring assemblies are highly effective in preventing such leaks in machines such as compressors, for example, when the compressor piston rod is in motion, they are less effective when the rod is at rest as when the compressor is inactive. Some industrial compressors, such as those used in pumping stations along natural gas transmission lines, remain in a static or inactive condition for much longer time periods than they are actually in use in the compression of gas. As a result, significant volumes of gas can be lost to atmosphere through the rod packing of these machines during their long periods of inactivity. The problem has become more significant in recent years due to the substantial increases in the cost and value of natural gas that have occurred.
There are several possible reasons why these prior art packing rings tend to leak at substantially greater rates when the machines in which they are used are inactive than when operating. First, the presence of lubricating oil under pressure in the spaces between the moving piston and the packing rings is believed to impede gas leakage. Thus when the machine is shut down with a consequent loss of pressurized lubricating oil, gas leakage can increase. Changes in piston rod alignment and in the shape of the sealing rings following shutdown of the machine as a result of temperature changes may also contribute to increased gas leakage.
By means of my invention, these and other problems encountered in the use of prior art packing rings are substantially overcome.